1. Field of the Invention
This invention relates to an endoscope apparatus having at the tip of its inserting section a detection means for detecting physical or chemical changes.
2. Description of Related Art
In place of the fiber-type endoscope, which transmits optical images through an optical fiber, an electronic endoscope utilizing a photoelectric-conversion-type image sensor is beginning to find its way into the market, due to its multifunctional character. However, the electronic components inside such an electronic endoscope, including the image sensor, are rather sensitive to environmental conditions, such as temperature, humidity and disinfectant gas, so that when placed under any severe condition for a long period of time, the electronic components may become irreparably damaged.
The flexible sheathing tube of an endoscope consists of a rubber tube having a bendable structure, so that it, particularly, is subject to generation of cracks or pinholes, through which water is likely enter. Also, when sterilizing the endoscope with a disinfectant gas, intrusion of gas may occur through these cracks or pinholes, resulting in the electronic components inside the electronic endoscope, in particular, the semiconductor devices, being damaged. Further, any cracks or pinholes may allow infectious, disease-causing organisms to get into the electronic endoscope during an operation; therefore, the endoscope cannot be sufficiently sterilized by washing in antiseptic solution alone, and there is the possibility of a second patient being infected with a disease. In view of this, Japanese Patent Laid-Open No. 1991-236825 and Japanese Utility Model Laid-Open No. 1985-37301 have proposed endoscope structures according to which a humidity sensor is provided inside the endoscope, thereby detecting any leakage of water into the endoscope.
In the technical means described in Japanese Utility Model Laid-Open No. 1985-37301, in which any water leakage is detected by a humidity sensor provided in the tip section of the endoscope, the electronic components inside the electronic endoscope may become damaged to such a degree as to be irreparable by the time the sensor has detected the leakage.
In view of this, the endoscope described in Japanese Patent Laid-Open No. 1991-236825 adopts a structure in which the electronic components mounted in the electronic endoscope are collectively arranged in a waterproof structure forming an image sensor unit, with the humidity sensor being arranged on the external surface of this image sensor unit. The humidity sensor is connected to a water-leakage detecting circuit inside an endoscope controller through a dedicated signal line for leakage detection, thereby making it possible to transmit a water-leakage detection signal before the electronic components have been damaged by water leakage. With this prior-art technique, any water leakage can be repaired before the electronic components have been damaged thereby, thus enabling the image sensing unit to be used again.
However, the above-described prior-art technique has a problem in that the humidity detecting means is provided in the tip section of the endoscope, which means a dedicated signal line for humidity detection has to be separately provided. As a result, an increase in the diameter of the inserting section is inevitable as compared to that of an endoscope apparatus not equipped with such a humidity detecting means.
Apart from this, Japanese Patent Laid-Open No. 1985-69620 discloses an endoscope having a solid-state image sensing device in the tip section thereof, according to which at least one network tube is formed by a plurality of conductors which constitute outlet paths for image signals obtained by this solid-state image sensing device and inlet paths for drive signals for driving the solid-state image sensing device, with a bundle of light-guide fibers, an air/water-supply channel, or a forceps channel being inserted into this network tube. Due to this construction, the tube diameter of the inserting section is reduced as compared to that type of endoscope in which a plurality of conductors are arranged as separate channels, by the space occupied by those channels.